This is a Shannon award providing partial support for the research projects that fall short of the assigned Institute's funding range but are in the margin of excellence. The Shannon award is intended to provide support to test the feasibility of the approach; develop further tests and refine research techniques; perform secondary analysis of available data sets; or conduct discrete projects that can demonstrate the PI's research capabilities or lend additional weight to an already meritorious application. The abstract below is taken from the original document submitted by the principal investigator. DESCRIPTION (Adapted from the applicant's abstract and specific aims): The disorder of obstructive sleep apnea (OSA) has a high association with daytime hypertension. There is no direct evidence that OSA causes the hypertension, and this high association may be due to co-morbid features, such as obesity or age, which can independently raise blood pressure. This relationship between OSA and control of blood pressure could be more clearly established if studies were conducted in the absence of confounding variables. It is the broad, long-term objective of this study to use the chronically instrumented, tracheostomized dog to investigate the relationship between airway obstruction during sleep and regulation of blood pressure. Preliminary studies in this model have established that each period of airway obstruction and arousal is associated with an increase in blood pressure, and that repetitive airway obstruction and arousal can cause an increase in the baseline blood pressure that is sustained even after normal airway patency is restored. There are a number of peripheral and central neural inputs that will be stimulated by upper airway obstruction during sleep that may affect blood pressure. Specific Aim 1 will examine the contributions of chemoreceptors, lung afferents, nasopharyngeal afferents and negative feedback from baroreceptors in the integrated sympathoexcitatory response that increases blood pressure during a period of apnea in the sleeping dog. Specific Aim 2 will examine changes in blood pressure and sympathetic nerve activity that occur in the post-apneic period, in either the presence or absence of arousal, and determine whether arousal can transiently modify baroreflex function. Specific Aim 3 will examine the mechanisms by which repetitive airway obstruction over a single night can cause an increase in baseline blood pressure.